Different Types of Shift Registers and its Applications with operations

Shift register is a combination of flip flop only single bit of binary data i.e. 0 or 1. We need flip flop to store the multiple bits of binary data. Single flip flops are use to store only one bit of binary data. For store of “n” number of binary data we need an “n” number of flip flops because flip flop can only one bit of binary data. Flip flop are use to store information and construction of register r. The shift register is a device which is the group of flip flop for store of binary data. Example, if a computer is to store 16 bit binary data, it uses 16 flip flops. Register input or output may be serial and parallel, it is based on requirement. The binary data bits series store by register is called “Byte” or “word”. The bit length of Byte is 8 bit and length of word is 16 bits (or 2 Bytes).

When number of flip flop connects in series, it is called register. The store information transferred within register is called as ‘shift register’. It is a sequential logic circuit that can be used for the storage or the transfer of binary data on ever clock cycle.

• Serial-in to Parallel-out (SIPO) — The binary data loaded in serial, one bit at a time and the parallel data is available at the output side.
• Serial-in to Serial-out (SISO) — In this mode the data is serially shifted “IN” and “OUT” the data is shifted serially “IN” and “OUT” of the register, one bit at an every clock pulse in either a left or right.
• Parallel-in to Serial-out (PISO) — Parallel binary data is loaded into the register and the data shifted out of the serially at every clock signal.
• Parallel-in to Parallel-out (PIPO) — Parallel binary data is loaded into the register and the data shifted out of the parallel at every clock signal.

Serial-in to serial-out shift register

This shift register is similar to the shift-in parallel-out register, except the data was directly read in parallel form from output Q0 to Q2. In serial in to serial out is allowed to flow straight through register and out of the other end serially. Since it has only one input and one output port, the shifting of DATA in shift register one by one at a time in serially hence it is called serial in to serial out shift register or SISO. It is one of the simplest register in which have three flip flop, it has only two connection with the flip flop and one common clock pulse of all flip flop. In SISO register the DATA enters the left hand side of flip flop and the serial out taken from the right hand of flip flop and the sequencing clock signal (CLk). Ever clock pulse signal the data shifts to the next stage of flip flop. The logic diagram is shown below.

Working principle of 3-bit SISO shift register

Let us assume the DATA bit “011” sending in shift register in input.

Initially the status of D flip flop is low level Q0 Q1 Q2 =000. Now understand the operation of 3- bit serial in to serial out for.

Initially the all flip flop is zero level in the absence of clock signal Q0 Q1 Q2 =000. Here the serial output receive form the Q0, the LSB DATA bit received “1″ at 3rd clock signal and the MSB DATA bit received 5th of the positive edge clock pulse. Therefore, the 3 DATA bit required 5 positive edge clock pulses for produce a valid output. Similarly, the “N” DATA bit SISO shift register requires 2N-1 positive edge clock pulses signal in order to shift ’N’ bit information.

For more information clock below: shift-register